Refrigerating apparatus and method



June 2, 1936. I w. E. CARPENTER 7 2,043,190

, REFRIGERATING APPARATUS AND METHOD 7 Filed Sept. 10, 1931 4 Sheets-Sheet 1 /V /I/ ///l /l i6 'NVENTOR I WZziier E. C'aqbenier ra am 'ATTORNEYS i June 2, 1936. w. E. CARPENTER 2,043,190

REFRIGERATING APPARATUS AND METHOD 4 Sheets-Sheet 2 Filed Sept. 1o, 1951 48 INVENTOR WaiirE. Ca:

June2, 1936. w. E. CARPENTER 1 2,043,190

REFRIGERATING APPARATUS- AND METHOD Filed Sept. 10, 1931 4-Sheeis-Sheet s nu/inn,

INVENTOR I v Milk-Brig. C'm'pnier onusvs w. E. CARPENTER 2,043,190

REFRIGERATING APPARATUS AND METHOD June 2, 1936.

Filed Sept. 10, 1931- 4 Sheets-Sheet 4 n t 1181?? I. Ca17 2e nfel wand/64m ATTORNE Patented. June 2, 193$ direct and mesne assignments, to McCain Maier Corporation, Newark, N. J., a corporation of New Jersey Application September 10,1931, Serial No. 502,002

11 Claims. (c1. tie-91.5)

My present invention is concerned with the provision of apparatus for and methods of efficiently utilizing solidified CO2 or equivalent material for refrigerating purposes.

5 An object of the invention is to provide a method and apparatus which will be effective to maintain a uniform temperature in a refrigerated compartment where the intensely cold solid CO: is used either directly or through secondary heat transfer media to absorb the heat from the compartment. I A more specific object of the invention is t provide a refrigerating system using solid carbon dioxide as the primary refrigerating medium'and in such a manner that the continuously dwindling size'of the iceblock will have no effect upon the uniformity of temperature in the refrigerating compartment. In other words, assuming thata fifty pound block of ice is originally introduced into the system, the temperature of the refrigerated compartment will remain the same even when the ice has melted down to a pound or less. Another object of the invention is to prevent waste of a relatively expensive refrigerating medium, such for instance, as solid carbon dioxide. Concerning this object of the invention, it may be noted that refrigerated truck bodies when standing over night in a garage or 4 other storage space, should be kept cold and it has been common practice where solid 00: re-

frigerant has been used, to' effect refrigeration ofthe truck not only duringrunning but d ing storage by the CO2. In accordance with my invention, I'provide means whereby the refrigerating effect of the carbon dioxide ice is used to maintain the truck properly cooled during the day and at night the brine circulating pipes of the truck may be I hooked up directly to an ammonia plant at the factory in such a manner that any substantial sublimation of the .ice is prevented and refrigeration is effected through the cheaper medium of come unduly low and designed to quickly lower 50 the temperature when the system is called upon to temporarily absorb an unusual amount of. g

' of the apparatus, such for instance, as automatic means for insulating the bottom of the ice cake heat.

Another object of the invention is to rovide. a system of this character which, save for the Samuel charging of the carbon dioxide compartment, will be fully automatic in operation and will require the -use of only simple types of conventional control mechanism and regulating devices.

Another object is to provide apparatus of simple, practical construction which will be rugged and durable in use, boththe apparatus and the methods being suitable for the solution of refrigerating problems regardless of the sine o! the chamber to be refrigerated, and operative to maintain substantially uniform temperatures in i any chamber from the size-of a domestic ice box to the size of a' freight car.

Another object is to provide refrigerating methods whichwill permit any desired temperature from sub-zero Fahrenheit to above freezing point Fahrenheit to be uniformly maintained by a tremendous difference in temperature of the primary'refrigerating agent and the atmosphere of the chamber to be chilled.

refrigerating agent which is itself intensely cold;

In accordance with one embodiment of the inof high heat conductivity upon which the CO:

rests. This support member absorbs heat from the chamber to be refrigerated either directly or heat transfer medium, such for instance, as a through the intermediacy of a suitable secondary I closed brine circulating system. Where the heat exchange between this conductive cold plate and the cooled chamber is direct, I find that by proportioning the area of the cold plate and by con- I heating it to any desired number of supplemental radiating surfaces designed in accordance with the particular refrigerating requirements (if the chamber to be cooled, any desired temperature may be maintained. I have discovered that the ice will be-self-feeding in that it will burn off from thebottom directly against the support, I

means with substantially no diminution in cross sectionaiarea and will be eflective to absorb the requiredamount of heat until substantially the very last bit of the ice has been melted.

While an apparatus such as thatabove-dis cussed, represents an elementary form of the invention, I preferably utilize various refinements contact with the and plate when heat is to be absorbed.

I have furthermore provided in conjunction with this apparatus a secondary heat transfer medium, such for instance, as brine pipes which under normal conditions are cooled directly by the solidified C02. Such a piping system, when used in conjunction with a truck or the like, is preferably so valved that heat transfer between the brine and the solid C0: may be cut oil at night and the cold brine. from an ordinary ammonia plant circulated through the pipes by simply attaching a pair of hose connections from the ammonia plant intosuitable taps in the truck piping system.

One method of insulating the ice from the cold plate as the temperature of the compartment to be refrigerated reaches the desired minimum, is an automatically operated elevator for picking up the ice bodily and lifting it out of contact with the plate. Various thermostatically controlled mechanical devices may be employed in the actuation of the elevator, and if desired, the

pressure of the gas evolving from the ice itself may furnish the power for actuating the lift.

The invention may be more fully understood from the following description in connection with the accompanying drawings, wherein Fig. 1 is a vertical sectional view through an ice receiving compartment embodying the invention;

Fig. 2 is a top plan witlrthe cover removed;

Figs. 3 and 4 are perspective views showing modified forms of heat exchange plates;

Fig. 5 is a view partly in side elevation but principally in vertical section showing the container forming part of a thermostatically regulated cooling system and utilizing the CO: gas which evolves from the ice to supply the power necessary for moving the ice out of contact with the cold plate;

Fig. 5a is a fragmentary view mainly in vertical sectionillustrating another method of control in which the auxiliary cold plates are thermostatically moved into and out of conductive relationship to the bottom of the'casing;

Fig. 6 is a fragmentary vertical sectional view through the bottom of the ice compartment illustrating an alternative method of operating the ice lift;

Fig. 7 is a vertical sectional view illustrating another type of control apparatus for actuating .the ice elevator, this view being highly diagrammatic insofar as the illustrating of the regulating mechanism is concerned Fig. 7a is an enlarged schematic view of the switch mechanism 10 but showing the switch at right angles to the position illustrated in Fig. 7. Inasmuch as this switch is of entirely conventional character, most of the structural details thereof, such as the energy storing spring and the switch arm tripping and stopping mechanism have been omitted for the sake of clarity.

Fig. 7b is a sectional view through theswitch mechanism taken approximately on the line Ia-Ia of Fig. lo. I

Fig. 7c is an enlarged side elevational view of the cam 83;

Fig. 8 is a perspective view of one form of elevator which may be utilized;

Fig. 8a is a perspective view illustrating a modifled type of elevator;

Fig. 9 iso. view partly insection and'partly in elevation showing the manner in which the C0:

view of the compartment between' the solid CO2 and the chamber to be cooled is effected through a secondary heat transfer medium;

Fig. 11 is a diagrammatic view of a generally similar system but illustrating the control mecha- 10 nism for the pump and means for cutting off heat exchange between the CO: and the refrigerating compartment and circulating brine from an ammonia plant during storage periods of the truck.

Referring first to Figs. 1 and 2 of the drawings, I have shown a CO: container C, constructed in accordance with one form of the invention. This container has side walls ill of good heat insulating material and is provided with a cover II, also of heat insulating material, the cover 20 being removable to permit charging of the container with a block of CO2 ice. The container bottom is formed of material which is highly heat conductive, such for instance as the relatively heavy cast aluminum plate l2, this plate defining 25 an upwardly facing shoulder l3 ,upon which the sides of the container rest, the insulated side walls being secured as at H to the cold plate I2; With this type oi. construction, the ice is substantially insulated against heat exchange by 30 radiation with the outside of the compartment, except through the cold plate l2 and in use, the ice will burn off at the bottom as it absorbs heat from the cold plate. In this figure, I have not shown any means of controlling the gas which 35 is evolved upon sublimation of the solidified CO2. This gas may escape from under the cover II, although in practice, it is customary to deliver the cold gas into the compartment to be refrigerated. The rate of sublimation of the solid carbon 40 dioxide will be directly proportional to the heat transmitted to it through the plate l2, which will oil'er an unchanging cold surface to the compartment to be'refrigerated, regardless of the amount of solid carbon dioxide which is resting upon the 45 plate. The solid CO2 sublimates at a rate directly proportional to the rate of heat absorption by the plate I! and whether the ice piece be large or small, the temperature of the plate i2 will remain uniform and the temperature of the chamber which is chilled by the plate, will likewise remain uniform. The frosting and defrosting of the plate will automatically prevent over refrigeration or under refrigeration.

In discussing uniformity of temperature, I of course, imply the maintenance of temperature within a veryclose range. Obviously the temperature of the compartment may be suddenly raised by the influx of warm air, but in such an event, the rate of sublimation of the CO: is 60 almost instantly increased and the temperature of the compartment brought back to normal. In Figs. 1 and 2 I have not shown the compartment to be refrigerated but it will be understood that this compartment may be of any desired size and (i5 shape and the container may be disposed at any suitable location therein. When used in connection with a truck or freight car, the cover Ii of the ice compartment preferably is in the nature of a hatch in the roof of the truck or car through 74 which the ice may be introduced.

In predetermining the heat absorbing area of the plate I2, I may resort to the use of any suitable number of additional cold plates in intimate contact with the plate I! and serving to increase 75 laterally projecting bottom portion of thecasting l2. Plates I! are bolted, welded or otherwise tightly secured against cold plate l2 to promote good heat conductivity, and in practice, the supplemental plates I! are kept at a temperature which is substantially identical with that of the plate I2. Frosting of the plate occurs uniformly over the exposed surfaces of the plate I2 and the plates IS. The number of the plates I! used and the area thereof, is proportioned in accordance with the refrigerating requirements of the particular chamber to be chilled and in accordance with the temperatureat which the chamber is to be maintained.

In Fig. 3 I have illustrated a slightly modified type of supplemental cold plate Iia which is provided with fins l'l thereon to increase the heat absorbing surface area.

In Fig. 4 I have shown another modified form of supplemental heat exchange plate lib adapted sure in the diaphragm chamber sufficiently to to promote the circulation of air in the refriger ated compartment. The plate in this instance. is in the form of a louvre having a numberof openings l8 therein with the projecting air current directing hood portions extending forwardly and outwardly over the openings.

In Fig. 5 I have illustrated. a refrigerating system employing substantially the same type of container C as that illustrated in Fig. 1. Here,

however, the container cover 2ll is clamped in place and a pop valve 2! is mounted in the cover to prevent the generation of unduly high gas pressures in the chamber. A mounting plate 22 is fixedly secured in any desired manner, not shown, below the chamber C and one end of this plate serves as the rigid bottom of a diaphragm chamber, the chamber being completed by a flexible diaphragm 23, the edges of whichare bolted down against one end of the plate 22, illustratively by the bolts 24, urging the clamping ring 23 against the edges of the diaphragm. In this case, a suitable recess 26 is provided in the upper is. flexible tubing 33 into the diaphragm chamber,

from whence it escapes through an exhaust pipe 34.

A bellows type thermostat has one end fixed to a bracket 36 attached to the under surface of the plate 32. A needle valve 31 adapted for coaction with a valve seat 33 at the end of the exhaust pipe 34 is provided with a stem 39 extending through the thermostat and attached to the free end thereof as at 40.

The operation of this system is as follows:-

Under normal conditions, the ice rests directly on thecold plate and the chamber to be refrigerated is cooled directly by. the cold plate 21 and the supplemental plates l5. Thega's which'evolves upon sublimation of the ice, escapes into the diaphragm chamber and through the exhaust pipe 34,

able for refrigerating the chamber.

discharging into the the chamber to be refrigerated and aiding to cool the same. -Whenever the temperature of the, chamber to be refrigerated is sumciently lowered, the thermostat 35 con- ,tracts, moving the needle valve 31 into position up off the cold plate and substantially insulated therefrom by the gas which surrounds the block.

It will be apparent that the same pressure obtains in the chamber C as the pressure which obtains in the diaphragm chamber, but the elevator itself, as well as the ice being under balanced pressures, are lifted by the effective unbalanced pressure applied over the surface of the diaphragm.

When the elevator is in raised position, it will I ,be obvious that there is no escape for the gas except through the pop valve 2|. This valve, however, opens only under a relatively high pressure, so that if the needle valve 31 remains closed for a considerable period of time, valve 2| will merely open momentarily to blow of! excessive gas pressures without releasing the prespermit the elevator to drop under the weight of the ice thereon.

As soon as the refrigerated chamber starts to warm up again, the needle valve .31 is thermostatically ,withdrawn, thereby relieving pressure in the diaphragmchamber and permitting the elevator with the ice which it supports, to again drop into contact with the cold plate 21, whereupon the rate of ice sublimation will be accelerated and the same cycle of cooling the chamber andthermostatically closing the needle valve repeated.

In Fig. 50. -I have illustrated another method of thermostatically regulating the rate of sublimation of the soldified CO2. In this case, in-

stead of attempting to bodily elevate the ice from the primary cold plate, I utilize mecha-v nism for automatically moving the auxiliary plates lid, out of engagement with the primary cold'plate l2d. v

The cold plates I5d in this instance, have their upper edges hingedly connected as at I20 with the heat insulating side walls I2I of the CO2 container. The lower edges connected as at I22 to the outer ends of toggle levers I23, these le-- vers having their inner ends pivotally connected to a spider element I24 having a hollow hub which slides upon a pin I25, projecting downwardly from the cold plate l2d. The spider member I24 which actuates the toggle levers, is

moved back and forth upon its mounting pin I I25 by a thermostatic bellows I26 .connected by a push pull rod I21 with the spider.

The modus operandi of this type of control mechanism is as follows:

When the temperature of the chamber to be refrigerated falls below apredet-ermined minimum, the contraction of the thermostatic bellows acts through the push pull rod I21 to elevate' the spider I24, tending to straighten out the toggle levers I23 and to swing the lower ends of ,the plates lid out of heat conducting relationship with the primary cold plate l2d, thereby toward collapsed position and to thereby draw a be apparent from Figs. 7a and 7b. From this Fig.6 shows a simple arrangement for operating an ice elevator 4|. Here the lifting rod 42 of the elevator passes through the cold plate 43 and has its lower end secured to a cross frame or plate 44. A coiled contractile spring 45 encircles the rod 42, one end of this spring being anchored as at 46. to the cold plate and the other end of the spring being anchored as at 41 to the plate 44 so that the normal tendency of the spring is to draw the plate 44 upwardly and maintain the elevator 4| off the floor of the container. A circular bellows type mercury thermostat 48 is mounted on the plate 44, encircling rod 42 and its spring 45. The bellows tends, when the cold plate.

expanded by heat, to force the plate 44 downwardly against the action of the spring 45 and thereby let the solidified CO: come to rest upon In order that the thermostat 48 may be substantially unaffected by direct contact with the cold plate, it preferably carries a circular protective plate 49 of heat insulating material for engagement with the cold plate.

The cycle of operation of this form of apparatus is as followsz-When the temperature of the chamber to be refrigerated is above the temperature desired, the bellows 48 will depress the elevator 4| and drop the solid CO: against the cold plate, which in this instance, I have designated as 21a. when sub-normal temperatures obtain in the chamber to be refrigerated, the

contraction of the bellows will permit the spring 45 to lift the elevator 4|, thereby moving the CO2 out of contact with the cold plate and retarding its rate of sublimation.

In Fig. '7 I have shown an alternative type of control system in which the elevator 60 may be moved up and down by mechanism operated from a thermostatically controlled motor.

62 at its lower end, resting upon a cam 63 carried 'by cam shaft 64 driven through a suitable reduction gearing 65 from an electric motor 66. The motor may be energized from the usual storage battery 61 of a truck, the truck being fragmentarily illustrated at 58 in this view, and the cover 69 of the CO: compartment is in the form of a hatch in the roof of the truck. Arranged in the motor circuit is a standard four pole or double two pole two-way snap switch 10 arranged to revolve with the. cam shaft. This switch is controlled by a four point, double ended tilting mercury switch 1|, which is also of conventional construction and is merely diagrammatically illustrated. The mercury switch is tilted back and forth by a lever train 12 actuated from a thermostatic bellows 13. In operation, the two pairs of arms 14 and 15 of the snap switch are latstorage spring and arm detent and check mechanism which is not herein illustrated inasmuch as the switch itself its standard construction and the switch, per se, is not my invention. The contacts for the arms 14 and" are so arranged that whenever one arm is moved into neutral ltion, the other arm is moved to brids it! two contact points.

The manner of operation of the device Here the plunger rod 6| of the elevator carries a roller position, it will be noted that the four point mercury switch 1| has been tilted in a counterclockwise direction and that the motor circuit has been completed through the contact members 15a, 15a. After the motor has turned onequarter of a revolution and thereby elevated the lift 60 through one of the high sides of the cam 63, the snap switch mechanism will switch the arm 15 to a neutral position and swing the switch arm 14 into the contact bridging position of Fig. 7a. No motor circuit, however, can be completed through the arm 14 due to the fact that the mercury switch 1| is at this time opencircuited. When the mercury switch is again thermostatically tilted to establish a circuit to the motor through the switch arm 14, the motor will again make one-quarter turn, permitting the lift 60 to drop as one low side of the cam passes thereunder and upon the completion of the onequarter turn of the cam shaft 64, switch arm 14 will snap to a neutral position while the switch arm 15 snaps into position to bridge its contacts. At this time, however, the motor circuit is again opened at the thermostatic switch and it will not be closed until such time as the necessary temperature variation in the chamber to be refrigerated has acted through the thermostat to again tilt the mercury switch. i

In other words, when the thermostat 13 condirection, it will close the motor circuit through the four pole or double two 'pole, two-way snap switch and the motor will run until the cam shaft 64 has made one-quarter revolution, whereupon the snap switch will cut out and further operation of the motor is prevented until the thermostatic switch H is tilted in the opposite direction under the influence of the thermostatic bellows, whereupon the motor will again be cut into circuit and the cam shaft advanced another quarter revolution. It will be seen from the side view of the cam (Fig. 70) that one quarter revolution of its shaft is sumcient to cause it to either raise or lower the elevator as the case may be. Obviously, the elevator is raised upon contraction of the bellows 13 and lowered upon the expansion thereof.

Fig. 8 shows in perspective the elevator 60 which is of generally star shape in order to aiford adequate surface contact with the ice. The elevator which is of heat conducting material, fits very snugly into its recess 60a in the cold plate so that when the elevator is lowered, it is in intimate heat exchange relationship with the cold plate and the desired burning oif of the ice block bottom is effected. Fig. 9 shows an alternative form of elevator I60, which is of square cross section.

,ing one of my casing units 0, having its cold plate directly attached toa hanger unit as, mounting a plurality of shelves 9| in which freezing trays 92 for ice cubes, are supported.

In Fig.- 10 I have shown the invention as applied to' another and somewhat modified embodiment of the invention used for refrigerating a truck body B. Here the ice chamber C has a cover I" in the form of a hatch-way in the roof of the truck and the cold plate |B| is in the form of a hollow casting connected at opposite sides with the two ends of a closed piping system I02 containing brine. It is within the scope of my invention to employ a themeof the system and operated in any suitable man-- ner to maintain a continuous or intermittent brine circulation. The regulating devices and the actuating means for this pump are not illustrated in Fig. 10, but it may be conveniently operated in the same manner as the pump which I have shown in connection with thedisclosure of Fig. 11, which I shall now describe.

With this form of the invention, the ice compartment C is completely insulated and a closed system of piping I05 includes pipe coils lying within the bottom of the chamber C and upon which the blockof CO: rests. The piping within the chamber C may, if desired, be provided with fins I05a or its eflective heat exchange area may be otherwise increased. At each side ofthe pipe coil which lies within the chamber C I provide a shut off valve I06 and when these valves are closed, a partial brine circulation may be maintained by tapping in an inlet line I01 and an outlet line I08 through suitable extensions I09 arranged at spacedpoints in the piping system I05 and normally closed by suitable valves IIII. When the valves I06 areclosed and the valves H0 opened, and the hose connections I01 and I00 from an ordinary ammonia plant 'hooked on to the system, it will be observed-that there will be substantially no sublimation of the CO ice since this ice is housed in a completely insulated chamber and no brine can circulate in that section of the piping system'l05 which is arranged between the valves I06. Thus a truck standing idle at night, may be hooked up to an ordinary ammonia plantand kept cool while the expensive CO: refrigerant is substantially pre-j served against doing any work. When the truck is running during the day delivering ice cream or other frozen commodities, the valves H0 are closed, the hose connections I08 and I01 re- 7 moved and the valves I06, I06 opened. Even in the absence of a circulating pump, there would be a thermo-siphonic circulation of brine chilled by the intimate contact between brine pipesv within the refrigerating chamber and the solid CO2. Such a thermo-siphonic circulation would be effective to maintain a substantially uniform temperature in the truck body due to the cold storing ability of the brine. An even more accurate regulation, however, may be effected by thermo-siphonic circulation thereof, will be substantially quiescent in the pipes and there will be substantially no heat delivered to the CO2 ice. If the truck body starts to warm up, the

thermostatic switch II4 can close, cutting off the motor and operating the pump so that the brine is circulated through the chamber C and the heat which has been absorbed by the brine, is quickly absorbed by the CO2.

I refer to brine in its most generic sense, it

being merely necessary to provide some solution which will not be frozen in the pipes the solid C0: and which has a cold storing prop 1 erty. One advantage of using a brine, particularly a brine of the same character commonly used in an ammonia plant, is the fact that there is no need for draining the brine systems when hooking up the connections I01, I00, that is to say, the brine circulating pipes of an ammonia system may be hooked directly on to the brine .circulating pipes of the truck system with a minimum amount of trouble and eflort.

Itwill be observed that in many of the various systems illustrated,I have omitted all showing of supports for the control mechanism and all means for utilizing the refrigerating effect of the 00: gas. In practice, however, this gas will be directly or indirectly vented into the chamber to be cooled so that the maximum refrigerating value of the ice may be utilized. Entirely regardless of the manner in which the gas exhaust is handled, all forms of theinvention provide means for most effectively obtaining di rect or indirect heat interchange between the intensely cold CO: ice and the chamber to bechilled and in every event, unnecessary waste of the ice and over refrigeration of the'chamber is prevented.

It is' within the scope of my invention to utilize various intensely cold refrigerating mediums other than solidified CO: and I intend that the term solid CO2 shall be construed as embracing all refrigerants which are equivalent for pur- It will thus be seen that there is herein described apparatus and methods in which the several features of this invention areembodied, and which apparatus and methods in their action, attain the various objects of the invention and are well suited to meet the requirements of practical use.

As many changes could be made in the above construction and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, itis intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:-

l. I A method of refrigeration which consists in depositing a substantially solid block of carbondioxide upon a support means of high heat conductivity and preventing heat exchange between said block and the region to be refrigerated except through said conductive means, and automatically reducing the rate of heat exchange be tween said means and the block, by lifting the block out of engagement with said means when the temperature of the region to be refrigerated has been reducedto a predetermined extent.

2. Refrigerating apparatus of the class described including a container for solid carbon lift solid CO: oil! its support and mechanism to actuate the elevator and a thermostat for con-- trolling said mechanism.

3. Refrigerating apparatus of the class described including a'container for solid carbon dioxide, said container being completely insulated except at the portion thereof which sustains thecarbon dioxide, said sustaining means being of high heat conductivity and in heat exchange relationship with the region to be refrigerated, whereby sublimation of the CO2 occurs substantially entirely at the surface of the CO: which is in contact with said conductive means, means for breaking the contact between the CO2 and the conductive means when the temperature of the refrigerated region has been reduced to a predetermined point and means for re-establishing the contact when the temperature has increased to a predetermined point, said making and breaking means including an elevator adapted to lift solid CO: off its support and mechanism to actuate the elevator and a thermostat for controlling said mechanism, said mechanism including an elevatoroperating means, said means including an expansible shell through which the gas sublimating from the CO: is normally exhausted and a thermostatically controlled valve for closing the exhaust and permitting the CO2 gas pressure in the chamber to actuate the elevator.

4. Apparatus of the character set forth in claim 3 and wherein a safety blow-oil valve is provided in the solid CO: container to relieve unduly high gaseous pressures when the thermostatically controlled valve is closed.

5. Apparatus of the character set forth in claim 3 and wherein a safety blow-off valve is provided in the solid CO2 container to relieve unduly high gaseous pressures when the thermostatically controlled valve is closed, said safety valve operating only at pressures in excess of those required to actuate the elevator.

6. Refrigerating apparatus of the class described including a container] for solid carbon dioxide, said container being completely insulated except at the portion thereof which sustains the carbon dioxide, said sustaining means being of high heat conductivity and in heat exchange relationship with the region to be refrigerated, whereby sublimation of the CO: occurs substantially entirely at the surface of the CD: which is in contact with said conductive means, means for breaking the contact between the CO2 and the conductive means when the temperature of the refrigerated region has been reduced to a predetermined point and means for re-establishin'g the contact when the temperature has increased to a predetermined point, said making and breaking means including an elevator adapted to lift solid C0: of! its support and mechanism to actuate the elevator and a thermostat for controlling said mechanism, the actuating mechanism including a motor operated cam and a switch for the motor and a thermostat to actuate the switch.

'7. Refrigerating apparatus of the class described including a container for solid carbon dioxide, said container, being completely insulated except at the portion thereof which sustains the 5 carbon dioxide, said sustaining means being of high heat conductivity and in heat exchange relationship with the region to be refrigerated, wherebysublimation of the CO: occurs substantially entirely at the surface of the C0: which is 10 in contact with said conductive means, operating means including a spring normally operated to lift the elevator and a thermostat including temperature sensitive apparatus to oppose the action of the spring when the temperature in the re- 15 frigerated region exceeds a predetermined minimum.

8. A method of refrigeration which consists in cooling a chamber to be refrigerated by heat exchange between said chamber and an encased 29 supply of solid carbon dioxide through the intermediacy of a highly heat conductive support for the encased carbon dioxide and utilizing the temperature of the compartment to be refrigerated to regulate the rate of heat exchange between the solid carbon dioxide and the support, by lifting carbon dioxide bodily off its support when the temperature of the chamber to be refrigerated is reduced to, a predetermined minimum.

9. In a refrigerating apparatus of the character described, a container for solidified CO2, said container including CO2 support means of high heat conductivity and adapted for disposal in heat exchange relationship with the chamber to 35 be refrigerated, means substantially preventing heat exchange by radiation between the CO2 and the chamber to be refrigerated except through said support means, complementary heat absorbing means movable into conductive relationship with said support member and means thermostatically controlling the movement of the secondary heat absorbing means into and out of such conductive relationship with said support member.

10. Apparatus as set forth in claim 9 wherein the support means comprises a metal plate serving as the bottom of the container and the secondary heat absorbing means including metallic members arranged exteriorly of the container and movable into and out of engagement with the plate. v 11. In a refrigerating apparatus of the character described, a container for solidified 00:, said container including CO: support means of high heat conductivity adapted for disposal in heat exchange relationship with the chamber to be refrigerated and constituting a primary means for absorbing heat from said chamber to herefrigerated, means substantially preventing heat an exchange by radiation between the CO2 and the chamber to be refrigerated, except directly through said support means, a secondary heat absorbing means disposed within the chamber and capable of transmitting heat to said C0: only through said support means, and means thermostatically operable to effect relative movement of said primary and secondary heat absorbing means into or out of conductive heat exchange relationship with each other.

WALTER E. CARPENTER. 

